This invention relates generally to a fluid restriction tool used primarily when fishing while running or lowering washover pipe in a well bore and an automatic blowout preventer. The fluid restriction tool prevents fluid runovers by controlling the flow of fluid from the washpipe into the work string (which is above the washpipe) through the washover pipe and permits the lowering of a wireline tool through the fluid restriction tool without hanging it up on the fluid restriction tool. The tool also functions as a safety valve to prevent well blowouts.
When a drill string or production string becomes stuck in a well bore it is common to perform fishing operations to retrieve the drilling string. A typical procedure for doing this is to run or lower washover pipe into a well bore. The washover pipe generally has a large inside diameter with a relatively close fit inside the well bore. As the washover pipe is lowered into the well, fluid in the well cannot displace fast enough around the outside of the washover pipe. Hence some of the fluid must be forced up through the inside diameter or passageway of the washover pipe. At the top of the washover pipe the inside diameter may be greatly reduced in the top bushing. When drilling fluid in the well is forced through the smaller inside diameter at the top of the washover pipe, the velocity of the fluid is generally greatly increased. This means that the fluid is traveling up faster than the pipe is being lowered. In this situation the fluid may run over the top of the work string before it reaches the point where the slips are set on the drilling platform. The slips are generally set when the drill pipe which is lowering the washpipe is two or three feet above the floor level of the drilling rig. In the situations where the drilling fluid has runover, it may runover as high as sixty (60) feet or more up in the derrick. Anytime the fluid runs over the top of the work string the runover creates hazardous working conditions, causes pollution and causes waste the of valuable fluids in the well. Additional waste results from the loss of drilling fluids, some of which are relatively expensive, and the rig down-time resulting from the occurrence of this hazardous condition.
In the past a method used to control drilling fluid runovers from wells has been to use what is commonly known in the oil field as a bleeder plug. A bleeder plug generally has a pin connection the same as the connection on the work string and usually the same inside diameter as the connection on the work string. Normally about one or two inches above the threaded portion of the bleeder plug a flat metal plate is welded. A half-inch valve is connected on the plate and a bail about twelve (12) inches high is welded to the bleeder plug which acts as a handle to chain the plug to the hook just below the traveling blocks.
The bleeder plug only partly controls the washover because the bleeder plug generally cannot be always used with running drill collars. Drill collars generally have to be handled with what is commonly known in the oil field as a handling sub or a lift nubbin which has no connection for a bleeder plug. Drill collars generally have a relatively large outside diameter and a fairly small inside diameter. This may cause a great deal of displacement of drilling fluid as the drill collars are lowered into the well containing the drilling fluid. The drill collars are placed in the washover string above the jars and bumper jars which are fishing tools. This is near the top of the washover pipe where they are usually screwed into a connection about a couple of feet above the washover pipe. The drill collars are generally about thirty (30) feet long.
Another method used in the past to prevent runover was to lower the washover pipe and drill collars very slowly. This is time consuming and as with most drilling may be very costly. The driller does not know how slowly to lower the drill collars and often a driller will get impatient and go too fast and in turn this forces the fluid over the top of the work string. When this occurs everyone on the floor of the drilling rig may be drenched with drilling fluid in addition to the loss of the fluid and the mess which occurs. Some of the drilling fluids are dangerous to the eyes and skin and some workers will not work under these conditions. Since the bleeder plug is chained to the hook this is dangerous to everyone on the rig floor because in the past some of these plugs have fallen from several feet up in the derrick for one reason or other when the chain came untied or the bail breaks. Also bleeding the fluid into the work string as it is being lowered keeps a lot of hydrostatic pressure off the formation and in turn is not as likely to break the formation down and lose fluid in the well bore. When fluid is lost in a well bore you lessen the hydrostatic pressure in the well bore. If there is any kind of high pressure zone of water, gas or oil, it is very likely the well will blow out.
With a bleeder plug very little fluid enters the bore of the work string, drill pipe or tubing since the bleeder plug has trapped air in the work string that is being lowered in the well bore, in turn this creates more hydrostatic pressure on the formation which is very bad.
Applicant is aware of the following U.S. patents:
3,151,688, Young; 3,446,237, Haley; 3,675,720, Sizer; 3,799,258, Tausch; 3,826,309, Tausch; 3,845,818, Deaton; 3,850,191, Brown; 3,865,141, Young; 3,951,338, Genna; 3,955,623, Aumann; 4,077,473, Watkins; 4,088,298, Brown; 4,129,184, Parker; 4,154,303, Fournier; 4,216,830, Fredd; 4,252,197, Pringle.
It is an object of the present invention to overcome the problems present in the prior art and provide an apparatus and method which allows workmen to safely lower a washover pipe into a well bore. It is another object of the invention to provide an apparatus and method which will prevent the loss of drilling fluid while lowering washover pipe in a well bore. It is another object of the invention to provide an apparatus and method which will protect workmen on the drilling rig floor while lowering washover pipe in a well bore. It is another object of the present invention to provide an apparatus and method which prevents fluid runover while permitting the insertion and withdrawal of wireline tools. It is another object of the invention to provide an apparatus and method which prevents runover of drilling fluid while permitting inserting and withdrawing a fishing tool therethrough to retrieve stuck pipe. Another object of the invention is to keep more hydrostatic pressure off the formation. It is another object of the invention to provide a safety valve means which allows insertion and retrieval of wireline tools. Other objects of the invention will be apparent from the following detailed disclosure.